Conventionally, in a rearview mirror applied to vehicles such as an automobile, a so-called “electrochromic mirror” which enables reduction of glare from the headlights of a following car at night by electrically changing the reflectivity thereof has been known (see, for example, Japanese Utility Model Application Publication (JP-Y) No. 62-2587).
As shown in FIG. 2, an electrochromic mirror 100 disclosed in JP-Y No. 62-2587 has a construction whereby thin films of a transparent electrode 104, iridium hydroxide (Ir(OH)3) 106, tantalum pentaoxide (Ta2O5) 108, tungsten trioxide (WO3) 110, and an aluminum (Al) electrode 112 are successively laminated on the back of a glass substrate 102 by means, for example, of vacuum deposition and, at the same time, a glass plate 114 for protecting the aforementioned respective thin films is applied to the side of the aluminum (Al) electrode 112 with a sealer (adhesive) 116. When a voltage is applied between the transparent electrode 104 and the aluminum (Al) electrode 112 by an electric source apparatus 118, the respective thin films of iridium hydroxide (Ir(OH)3) 106 and tungsten trioxide (WO3) 110 are coloring-reacted to change the reflectivity of the electrochromic mirror 100 (see arrow B of FIG. 2).
However, in this electrochromic mirror 100, unless film thicknesses and film qualities of the aforementioned respective thin films are balanced, a thin film that has been colored once does not revert to its original state in some cases. Moreover, since performance is sensitive to the influence of variations in the respective film thicknesses, difficult manufacturing conditions are imposed. Further, since the multi-layered film is formed by vacuum deposition, there is also a problem of high costs.
On the other hand, an electrochromic mirror having a construction whereby reflectivity is changed by a coloring reaction of a so-called “electrochromic solution”, which is an electrically colored solution, is also known (see, for example, Japanese Patent No. 2672083).
As shown in FIG. 3, in an electrochromic mirror 200 disclosed in Japanese Patent No. 2672083, two glass substrates 202 and 204 are disposed parallel at a constant interval, and transparent electrode films 206 are formed on respective internal surfaces facing each other of these two glass substrates 202 and 204. An electrochromic solution 210 is sealed in the interior of a space (cell) sealed with a sealing agent 208, between these respective transparent electrode films 206. Further, a reflecting film 212 and a protection coating film 214 are formed on the back (lower surface in FIG. 3) of the glass substrate 204. When a voltage is applied between the respective transparent electrode films 206 by an electric source apparatus 216, the electrochromic solution 210 is coloring-reacted, and the reflectivity of the electrochromic mirror 200 is changed.
However, in this electrochromic mirror 200, unless the two glass substrates 202 and 204 are applied parallel to each other via a sealing agent 206 with high precision, the image of reflected light (see arrow C in FIG. 3) from the reflecting film 212, and the image of the reflected light at a surface (the upper surface in FIG. 3) of the glass substrate 202 are not consistent, and a so-called double image is generated, leading to a mirror which is extremely difficult to see. In particular, a mirror for an automobile generally uses a curved mirror and, in this case, there are the drawbacks that manufacturing is extremely difficult, and costs increase.    Patent Reference 1: JP-Y No. 62-2587    Patent Reference 2: Japanese Patent No. 2672083